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Commit 1b15ec7a authored by Konstantin Khlebnikov's avatar Konstantin Khlebnikov Committed by Russell King
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ARM: 7912/1: check stack pointer in get_wchan 

get_wchan() is lockless. Task may wakeup at any time and change its own stack,
thus each next stack frame may be overwritten and filled with random stuff.

/proc/$pid/stack interface had been disabled for non-current tasks, see [1]
But 'wchan' still allows to trigger stack frame unwinding on volatile stack.

This patch fixes oops in unwind_frame() by adding stack pointer validation on
each step (as x86 code do), unwind_frame() already checks frame pointer.

Also I've found another report of this oops on stackoverflow (irony).

Link: http://www.spinics.net/lists/arm-kernel/msg110589.html [1]
Link: http://stackoverflow.com/questions/18479894/unwind-frame-cause-a-kernel-paging-error



Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarKonstantin Khlebnikov <k.khlebnikov@samsung.com>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 7c927322

arch/arm/kernel/process.c

+5 −2
Original line number Original line Diff line number Diff line
@@ -404,6 +404,7 @@ EXPORT_SYMBOL(dump_fpu); 
unsigned long get_wchan(struct task_struct *p)

unsigned long get_wchan(struct task_struct *p)

{

{

	struct stackframe frame;

	struct stackframe frame;

	unsigned long stack_page;

	int count = 0;

	int count = 0;

	if (!p || p == current || p->state == TASK_RUNNING)

	if (!p || p == current || p->state == TASK_RUNNING)

		return 0;

		return 0;
@@ -412,9 +413,11 @@ unsigned long get_wchan(struct task_struct *p) 
	frame.sp = thread_saved_sp(p);

	frame.sp = thread_saved_sp(p);

	frame.lr = 0;			/* recovered from the stack */

	frame.lr = 0;			/* recovered from the stack */

	frame.pc = thread_saved_pc(p);

	frame.pc = thread_saved_pc(p);

	stack_page = (unsigned long)task_stack_page(p);

	do {

	do {

		int ret = unwind_frame(&frame);

		if (frame.sp < stack_page ||

		if (ret < 0)

		    frame.sp >= stack_page + THREAD_SIZE ||

		    unwind_frame(&frame) < 0)

			return 0;

			return 0;

		if (!in_sched_functions(frame.pc))

		if (!in_sched_functions(frame.pc))

			return frame.pc;

			return frame.pc;